The Cell Resources Core (CRC) provides KCI members, and national and international cancer researchers, access to cell resources, most of which are unique and many of which are important to cancer research, as well as to services that enhance accomplishment of their cancer research. Originally established to provide iinvestigators the estrogen-responsive MCF-7 human breast cancer cell line and MCF10-A/F non-tumorigenic human breast epithelial cell lines, the scope of resources has expanded through the expertise of the current staff. New unique resources include a spectrum of MCF-10A derivatives with phenotypes in xenografts including preneoplasia by MCF-10AT, weak tumorigenicity by MCF-10AT1, carcinoma in situ by DCIS.com, and highly tumorigenic and metastatic MCF-10CA1a and CA1d cell lines. These lines constitute isogenic cells to examine breast neoplasia. Additionally, mortal fibroblast and epithelial cells and cell lines are available that were derived from human and mouse tissues including reduction mammoplasty and benign breast tissues, and human bile duct tumors. Services available include scientific consultation and assistance with development of new cell resources, toxicity testing for microchip gene expression analyses, clonogenic assays testing therapeutic response, and establishment of cultures from breast tissues. Benefits to Cancer Center Members include unique and reliable resources, the ability to develop new and unique resources, and the availability of specialized services. Also, the KCI benefits from stimulation of scientific interactions.